Bbc Brown, Boveri & Company, Limited

Andreas Furrer

Johann Ferdinand Milavec

Herbert Stemmler

Vaclau Mertl

A method for controlling the carrier of an amplitude-modulated transmitter, wherein a saving in carrier power with simultaneous minimum dynamic distortions is achieved by digitizing the useful signal and digitally processing all control signals. The circuit for carrying out the method contains a digital computing circuit which calculates from the digital amplitude values of the useful signal a carrier-control value which controls the carrier level via a digital switching amplifier.

Method and apparatus for controlling the carrier of an

A power switching amplifier for digital power amplification of an analog input signal, wherein the input signal range is subdivided into a plurality of equal voltage steps and a number, corresponding to the number of voltage steps, of switching stages is driven and their direct-voltage sources are connected in series. The association between the voltage steps and the switching stages is variable, such that all switching stages are uniformly loaded and the switching frequencies are reduced.

Switching amplifier for digital power amplification

A switching amplifier for producing large output power signals, including a plurality of amplifier stages having signal inputs driven in parallel and series connected outputs. The amplifier stages amplify pulse signals representative of an input signal with as little distortion as possible in a wide frequency band, and in particular exhibit very high insulation and very low capacity. The amplifier stages therefore include switching amplifiers each including a transformer having a toroidal core of low remanence material, a secondary winding formed of plural turns of rf stranded wire wound on the toroidal core, an insulating housing surrounding the secondary winding, a primary winding formed of plural turns of rf stranded wire disposed on the insulating housing, an outer housing confining the transformer and being filled with an insulating material, and a metallic mandrel within the bore of the toroidal core.

Switching amplifier

A switching amplifier including a plurality of switching stages, each having a drive transformer, the primary winding of which is separated from the secondary winding in a manner such that no conductive connection exists between them. The primary windings of each drive transformer is connected by means of controllable switching elements to a supply-voltage source in a push-pull circuit arrangement. The switching elements are controlled by means of a signal converter which converts an analog input signal into at least one pulse sequence which is applied to the control electrodes of the controllable switching elements by means of at least one control transformer having at least one primary winding coupled to the pulse sequence and plural secondary windings coupled to the control electrode of a respective switching element. The output terminals of the secondary winding of the drive transformer are connected to a full-wave rectifier. The push-pull circuit arrangement and the full-wave rectifier enable the switching stages to operate at a power output of virtually 100%.

A method of amplifying an analog low-frequency signal, and a switching amplifier implementing the method, wherein the maximum amplifiable voltage of the analog input signal is divided up into as many voltage bands as there are switching stages provided in the switching amplifier, and one switching stage is associated with each voltage band. Thereby the number of switching stages actuated and their switched-on period may be modulated in dependence upon the amplitude. In this way it is possible to reduce considerably the total number of switching processes during one period of the low-frequency input signal and the losses connected with each switching process.

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Turgi, Switzerland

Andreas Furrer